This invention relates generally to preparing coils of tubing, the tubing coils being especially suitable for use in medical equipment and medical devices in which compactly stored, tangle-free tubing is often extremely important. Various aspects of the invention include a method and an apparatus having means for dispensing a substantially uninterrupted stream of solvent through an extremely narrow orifice while automatically simultaneously tracking the orifice through a narrow band generally along tubing that has been coiled together in order to dissolve tubing surface and adhere such dissolved surfaces together where they are in contact with each other, another aspect of the invention being the weakly bonded tubing coil prepared in accordance therewith.
It has been known that, by coiling tubing into a helix and lightly adhereing together adjacent coils or turns, a portion of tubing several feet in length can be better handled during assembly of fittings to either end of the tubing, while packaging same into a compact unit, and when handling up to and at the point of use, such as in a hospital when the tubes are part of medical equipment or devices, for example, pressure monitoring or heparin infusion tubes for kidney dialysis machines, in blood bags for collecting and dispensing blood, and units for dispensing intravenous fluids, plasma, gases, or the like. When such a coil is to be put into use, it is removed from its package, and its ends are pulled apart so that the tubing is returned to a relatively straight length, free of knots, kinks and tangles.
Heretofore, commercial scale operations for coiling relatively stretchable tubing of the type typically used in medical equipment and devices, especially disposable medical tubing, have not been fully automated to the extent that the coil itself is automatically wound, a solvent is uniformly and automatically applied to the coil by mechanically synchronized tracking and dispensing, after which the solvent rapidly dries to adhere the individual turns together.
Equipment for automatically winding coils has long been is use, especially for winding coils onto bobbins or spools on which the wound coil is to be stored. Modification of such equipment makes possible the preparation of free-standing coils by winding on a mandrel, adhering adjacent turns together, drying as necessary, and removing the mandrel in order to prepare a coil that does not have a bobbin or spool therewithin.
Typically, such equipment will apply the solvent by spraying. Spraying often includes the incorporation of air or other gas into a liquid solvent so as to propel the solvent onto the coil, usually causing significant splashing and the application of much more solvent than is actually needed to adhere the coil together, thereby wasting solvent and substantially increasing the drying time needed, all of which are inefficient and costly, such being especially critical for preparing a relatively inexpensive item such as a length of tubing for which it is desired to minimize processing costs.
By the present invention, spraying of solvent is eliminated, the solvent being applied by dispensing in an extremely narrow stream near the surface of the coil by means of a narrow orifice such as that provided by a hypodermic needle, syringe dispenser, or the like, while simultaneously tracking that narrow stream in a narrow path generally parallel to the height of the coil. Then, capillary action spreads the solvent between the closely adjacent turns of tubing, whereby the very narrow path widens, but only after actual application of the coil, in order to form a broad adhesion band which extends on either side of the narrow path that was dispensed and tracked. The stream, which is entirely liquid solvent, is extremely narrow and of an amount having substantially no excess over that needed to just wet each turn at a location approximating a locus of points, this minimal amount encouraging the capillary action for spreading the solvent, capillary action conditions being enhanced when only minute amounts of liquid are confined within narrow pathways, such as those provided by the adjacent coils.
The unbroken stream of solvent according to this invention is applied substantially uniformly and without the use of any propelling gases, thereby substantially eliminating splashing and application of excess solvent to thereby minimize the amount of solvent needed, reduce the drying time significantly, and minimize the volume of exhaust or ventilation air needed in order to safely dispose of any solvent that volatilized into the surrounding air during the drying stage. Additionally, spraying the solvent with propelling and atomizing gases such as air evaporates some of the solvent before it reaches the coiled tubing, and the solvent reaching the tubing is a mist of droplets so small that much of the solvent evaporates before reaching the contact line between the adjacent coils, the intended point of application, thereby further wasting solvent.
It is accordingly a general object of the present invention to provide an improved method and apparatus for producing coils of tubing, and the tubing coils produced thereby.
Another object of this invention is an improved apparatus and method including a single mechanical structure for both dispensing solvent and traversing a solvent delivery path to the extent that the dispensing and traversing are inherently synchronized so that even if the dispensing rate varies during a given cycle or from unit to unit or over long periods of time, the amount of solvent delivered to each turn or coiled space is inherently uniform.
Another object of the present invention is an improved method, apparatus and product in which capillary action, rather than spraying, distributes solvent along the areas of contact between adjacent turns of tubing coil in order to reduce the amount of solvent needed to produce an adhered band in the coil produced.
Another object of this invention is an improved method, apparatus and product which includes squirting a very narrow path or locus of solvent along a coil by passing the solvent through a narrow orifice as it tracks along a wound coil.
Another object of this invention is an improved method, apparatus and product including use of a syringe that is tracked along a wound coil by the same mechanism that depresses the plunger of the syringe for dispensing solvent therefrom.
Another object of the present invention is an extremely efficient means and method for producing extremely efficiently even on a commercial scale, wound tubing coils having its turns weakly adhered together, by using extremely small quantities of uniformly applied solvent.